Common bacteria widely inhabit soils, rivers, lakes and marshes, etc. in the natural world. Consequently, there has been more interest in techniques being capable of sterilizing such common bacteria or making such common bacteria bacteriostatic without fail as well as being safe for the human body. Chlorine bactericides such as sodium hypochlorite, calcium hypochlorite, and sodium dichloroisocyanurate have been extensively used as bactericides/disinfectants in a wide range of environments. However, the use of such chlorine bactericides in large quantities have come to arouse troubles. For example, in factories and retail stores where food materials are handled in large amounts, cleaning with a sodium hypochlorite solution having a concentration exceeding 100 ppm is being conducted and this not only spoils the flavors of the food materials but also causes a problem that the sterilizing enhances danger (increase in trihalomethane (THM)).
It has recently become known that electrolytic water yielded by electrolysis is useful in the fields of agriculture, foods, etc. Attention is being directed to the excellent sterilizing/disinfectant activity of electrolytic water, and investigations are being made on the use of the water in clinical activities and in the home. Examples of the uses thereof which are being investigated include the sterilization/disinfection of diseased parts, incised parts, percutaneous openings for stationary catheters, etc. and the sterilization/disinfection of domestic utensils or articles, such as kitchen utensils, baby articles, and furniture, and house equipments, such as the toilet facilities and bathtub.
There are the following three kinds of electrolytic water which have been permitted as food additives.
(1) Weakly alkaline electrolytic hypo-water (additive name: electrolytic sodium hypochlorite water; 20-200 ppm; pH>7.5; electrolytically yielded from 0.2-2% aqueous sodium chloride solution using no diaphragm)
(2) Slightly acid electrolytic water (additive name: slightly acid hypochlorous acid water; 10-30 ppm; pH=5-6.5; electrolytically yielded from 2-6% hydrochloric acid using no diaphragm)
(3) Strongly acid electrolytic water (additive name: strongly acid hypochlorous acid water; 20-60 ppm; pH<2.7; yielded as anolyte water from 0.2% aqueous sodium chloride solution in a diaphragm type cell)
The acid waters among those kinds of electrolytic water have the following merits.
(1) The acid waters are superior in safety because THMs are less apt to generate under acid conditions.
(2) Resistant bacteria are less apt to generate and on-site management is easy.
(3) The waters can be used for treatment in combination with the alkaline electrolytic water.
(4) The waters can be utilized like tap water and impart no odor to the hands or fingers.
(5) Use of the waters just before suffices (sterilization time is short).
In the conventional treatment with sodium hypochlorite solutions, use of this chemical having a concentration up to 200 ppm as a food additive has been permitted. However, the addition thereof spoils the flavor and the chemical is apt to remain. In contrast, the electrolytic water has a high sterilizing effect even in a low concentration and is beneficial, although use thereof necessitates an initial investment in the production apparatus.
Such electrolytic water is obtained by electrolyzing water (raw water to be electrolyzed) to which a solute generating ions upon dissolution, e.g., sodium chloride, has been added, optionally together with an acid for pH adjustment. The electrolysis is conducted using either an electrolytic cell having an electrode pair consisting of an anode and a cathode or an electrolytic cell having a constitution comprising an anode, a cathode, and a diaphragm disposed between them.
Such an apparatus for electrolytic-water production is of a large scale and it is difficult to use it for more easily conducting sterilization/disinfection or the like in clinical activities or in the home. Under these circumstances, portable small electrolytic-water spray apparatus have been proposed (see references 1 to 3 given below).
[Reference 1] JP-A-2000-79393
[Reference 2] JP-A-2000-197889
[Reference 3] JP-A-2001-276826
Besides those, known techniques include JP-A-2004-129954 (an apparatus having a device generating the power necessary for electrolysis), JP-A-2004-130263 (the proportion of the inner volume of a piston to the volume, sectional area, etc. of a cell cylinder part is specified), JP-A-2004-130264 (raw water to be electrolyzed comprising a pH adjuster, surfactant, chlorine compound, and water is used to obtain electrolytic water having a pH of 3-8.5), JP-A-2004-130265 (the electrolytic water disclosed in JP-A-2004-130264 is used in a foamed state), JP-A-2004-130266 (the direction of voltage application to the electrodes is switched alternately), JP-A-2004-148108 (the voltage to be applied to the electrodes is made changeable), JP-A-2004-148109 (electrodes are disposed in a suction passage), JP-A-2003-93479, JP-A-2003-266073, JP-A-2002-346564 (separation type having a cylindrical electrode in a spray part), and JP-A-2001-47048 (gun type designed to be prevented from clogging in non-ejection periods; equipped with a motor).
However, the long-term use of hypochlorites for sterilization has yielded bacteria resistant to hypochlorite chemicals. The sterilizing effects of these chemicals have hence become insufficient and there is a doubt about the effectiveness thereof.
On the other hand, ozone-containing water has been placed on food additive lists and has gained approval of FDA (Food and Drug Administrations) of U.S.A. (2001) for use as a bactericide in food storage/production steps. Ozone-containing water has already come into many practical uses for sterilization in food factories and the sterilization of foods themselves. Recently, attention is focused on the fact that ozone-containing water is equal or superior in effect to sterilizing waters heretofore in use also in clinical fields such as dermatology, ophthalmology, and dentistry and is effective in reducing the burden to be imposed on the living body.
Ozone-containing water has the following two merits.
(1) The sterilizing effect of ozone (OH radical) is based on the oxidative destruction of cell walls and this indiscriminate activity is thought not to generate resistant bacteria.
(2) Ozone does not have residual tendency.
When ozone-containing water is used in combination with an oxidizing agent having residual tendency (e.g., a hypochlorite, persulfate, or percarbonate) according to need, a more effective sterilization treatment is possible.
Consequently, use of ozone-containing water can be one measure in eliminating the problem described above. However, there are drawbacks that the production of ozone-containing water necessitates a large apparatus and ozone-containing water does not last long. It has hence been difficult to spread ozone-containing water to general homes.